We perform a tomographic baryon acoustic oscillations analysis using the two-point galaxy correlation function measured from the combined sample of BOSS DR12 , which covers the redshift range of 0.2 < z < 0.75 .
Splitting the sample into multiple overlapping redshift slices to extract the redshift information of galaxy clustering , we obtain a measurement of D _ { A } ( z ) / r _ { d } and H ( z ) r _ { d } at nine effective redshifts with the full covariance matrix calibrated using MultiDark-Patchy mock catalogues .
Using the reconstructed galaxy catalogues , we obtain the precision of 1.3 \% - 2.2 \% for D _ { A } ( z ) / r _ { d } and 2.1 \% - 6.0 \% for H ( z ) r _ { d } .
To quantify the gain from the tomographic information , we compare the constraints on the cosmological parameters using our 9-bin BAO measurements , the consensus 3-bin BAO and RSD measurements at three effective redshifts in , and the non-tomographic ( 1-bin ) BAO measurement at a single effective redshift .
Comparing the 9-bin with 1-bin constraint result , it can improve the dark energy Figure of Merit by a factor of 1.24 for the Chevallier-Polarski-Linder parametrisation for equation of state parameter w _ { DE } .
The errors of w _ { 0 } and w _ { a } from 9-bin constraints are slightly improved when compared to the 3-bin constraint result .